If the artist is making credible threats to physically harm anyone then you should contact the police immediately.
As to posts, unless they are defamatory, there is little you can do. Even if they are defamatory, there is little you can do as a law suit is expensive and time consuming.
One avenue you may consider is to have a lawyer write a cease and desist letter to the person. While a cease and desist letter has little legal effect, it will tell the poster he could get in legal hot water which will cost him a lot of legal fees if nothing else.
You may want to discuss your situation with a lawyer in more detail. Most lawyers on Avvo, including myself, offer a free phone consultation.
This post is provided for general informational purposes only and is not intended to be legal advice specific to you. This general information is not a substitute for the advice of an attorney in your jurisdiction. The attorney client relationship is not established by this post.
If he is threatening you with harm, call the cops. You do not have a legal expectation of privacy in social media pages, no matter how many privacy settings you have--you can report him to the sites and see if they can block him (see if you can also block him yourself). If he is making false statements of fact, it could be defamation (slander is spoken defamation, libel is written defamation). However, opinions, slurs, insults and name calling are protected free speech.
"John is a big loser, the biggest idiot I've ever met. I hate him" is an opinion, insult, name calling and totally protected. "I saw Janet steal money from my purse" is statement of fact, which if false, can be defamation if you can prove economic damages as a result. If it is borderline, courts will always choose the first amendment over a personal dispute.
Also, truth is a defense to Defamation, so the Defendant will have the right to subpoena and depose people you know, and conduct discovery on every aspect of your life to prove the truth of what he said--If you value any modicum of privacy, this is not for you. Also, you have to show the court with proof by admissible evidence that you suffered economic damages as a result of Defamation.
You could hire a lawyer to send him a cease and desist letter, but it 's just a letter and he's not obligated to comply. It may just inflame the situation. You can try ignoring and blocking as much as you can.
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Your legal remedies are limited. First and foremost, I am hearing that you are in imminent serious danger of harassment. You should consider obtaining a c.258E anti-harassment order. If you are in fear of physical harm, contact your local police.
As for the comments themselves, it depends largely on their content. Take screen captures and review them with a lawyer to assess your options. You may also want to hire counsel to send 'take-down' notices to web sites with some of these comments, and/or directly notify social media sites that this user is abusing their policies, if they have any policies prohibiting this kind of conduct.
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